Evaporator

ABSTRACT

The present invention comprises an apparatus and method for evaporating a liquid to produce a product liquid and a vapor. Liquid is evaporated under the influence of a heat transfer medium in a heat exchanger comprised of a bank of tube plates formed from corrugated sheets. Vapor produced is separated from product liquid by a vapor collector which causes vapor to flow upward and into the collector from a downward-flowing product liquid and vapor stream. Backsplash entrainment into the vapor collector is prevented by an anti-backsplash device disposed between the vapor collector and a reservoir into which product liquid flows.

FIELD OF THE INVENTION

The invention relates to evaporating a liquid to produce a productliquid and vapor and to separate the product liquid from the vapor.

BACKGROUND OF THE INVENTION

Evaporators, or devices to evaporate liquids, generally include heatexchangers to transfer heat between a heat transfer medium, often steam,and the liquid. Various forms and types of heat exchanger designs exist,and they include a variety of means of promoting heat transfer betweenthe medium and the liquid. Forms and types of heat exchangers availablefor these purposes are generally complicated and expensive.

The production of high quality vapor and product liquid yield are primeobjectives of processes employing evaporators. Producing high qualityvapor requires effectively separating the vapor from the product liquid.Various kinds of vapor separation approaches exist which generally use avacuum or reduced pressure to extract the vapor into a vapor collectionsystem. In many designs, it is common for part of the product liquid tobe captured with the vapor in the process of vapor separation. This canoccur in at least two ways. First, some of the product liquid in theliquid-vapor mix flowing from the heat exchanger comprises drops whichcan easily be drawn into the vapor collection system. Second, as productliquid falls into a reservoir which is normally positioned below thevapor collection area, backsplash generates droplets which may beentrained into the vapor collector. When product liquid is drawn intothe vapor collection system, the vapor quality and product liquid yieldare reduced. Some vapor collection systems include further separation ofthe vapor and entrained product liquid, but these operations addsignificant complexity and cost. They also result in increased systemfootprint.

There are many different situations in which evaporators are useful forgenerating vapor and product liquid from a given liquid. A wide range ofoperating conditions and requirements require a large variety ofthroughput capacities and separation efficiencies. Designing tailoredsystems for particular situations is costly. Cost advantages can berealized when relatively inexpensive packaged systems are made availablein a modularized form in which multiple units can be assembled togetherto produce a system suitable for a particular application.

SUMMARY OF THE INVENTION

The present invention comprises an evaporator for evaporating a liquid.The evaporator includes a housing which facilitates the assembly of theevaporator and provides an integrated package for the evaporator. A heatexchanger is included in an upper portion of the housing to transferheat from a heat transfer medium, usually steam, to the liquid suppliedto the heat exchanger. Positioned below the heat exchanger andsubstantially within the housing is a vapor collector which includes avapor inlet having a downward-facing portion. Product liquid and vaporproduced in the heat exchanger flows downwardly, passing an upperportion of the vapor collector. Vapor flows upwardly into the vaporinlet and product liquid flows to a reservoir.

In another embodiment, the present invention comprises an evaporatorwith a housing, a heat exchanger for evaporating a liquid and generatinga product liquid and vapor, a vapor outlet disposed below the heatexchanger for permitting vapor to exit the housing, and a reservoirlocated below the vapor outlet to receive the product liquid. Ananti-splash device is disposed between the vapor outlet and thereservoir for preventing backsplash of product liquid from the reservoirinto the vapor outlet.

In yet another embodiment, the present invention includes housing, aheat exchanger for evaporating a liquid to produce a product liquid andvapor, and a vapor outlet located substantially below the heatexchanger. The heat exchanger is comprised of a bank of spaced-aparttube plates, and each tube plate includes a pair of corrugated sheetssecured together. Each corrugated sheet is formed as series ofalternating concave and convex segments with adjacent segments beingmirror images of each other. A tube plate is formed by aligning the pairof sheets so that each concave segment of one sheet faces a concavesegment of the other sheet forming a generally elongated tubular openingthere between. Likewise, opposing each convex segment of one sheet is aconvex segment of the other, the sheets contacting each other along aline. The sheets are secured together along lines of contact, andtubular openings are thus formed and bounded by the opposing concavesegments.

Other objects and advantages of the present invention will becomeapparent and obvious from a study of the following description and theaccompanying drawings which are merely illustrative of such invention.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a sectional view of the evaporator of the present inventionshowing the heat exchanger, vapor collector, and anti-splash device.

FIG. 2 is a perspective cutaway view of the heat exchanger plate.

FIG. 3 is a horizontal sectional view of the evaporator.

FIG. 4 is an exploded view of a tube plate that forms a part of the heatexchanger of the evaporator.

FIG. 5 is a perspective view of a tube plate.

FIG. 6 is an enlarged view of the encircled area shown in FIG. 3 andindicated by VI.

FIG. 7 is a schematic diagram of an evaporator made up of a series ofmodules in a multiple effect arrangement.

FIG. 8 is a schematic diagram of an evaporator made up of a series ofmodules in an alternative multiple effect arrangement.

FIG. 9 is a schematic of an evaporator made up of a series of modules ina single effect arrangement.

DESCRIPTION OF THE INVENTION

The present invention is directed at an evaporator to evaporate a liquidL and produce a product liquid PL and a vapor V. As shown in FIG. 1, theevaporator, indicated generally by the numeral 10, comprises a housing20 that contains components of the evaporator and facilitatesconnections to some of the components. A heat exchanger 30 is disposedwithin housing 20 for evaporating the liquid L, generating a mixed-phasestream including product liquid PL and vapor V. Disposed generallybeneath heat exchanger 30 is a vapor collector 40, a portion of which inone embodiment extends across housing 20. A reservoir 50 is positionedbeneath vapor collector 40 to receive product liquid PL. Disposedbetween vapor collector 40 and reservoir 50 is an anti-splash device 60for preventing backsplash from entering the vapor collector.

As further illustrated in FIGS. 1-3, housing 20 comprises a tubularstructure which is elongated and generally oriented in a verticaldirection. Housing 20 includes a wall 22 that encloses an interior area25, and end flanges 23. Housing 20 may comprise segments adapted to beconnected together using flanges 23. Moreover, flanges 23 permitcoupling evaporator 10 to other components of a system of which theevaporator is a part, including modular arrangements which will bediscussed later in this description. A liquid container 21, disposed inupper portion 22 of housing 20, holds liquid L and fluidly connects toheat exchanger 30 for facilitating flow of the liquid into the heatexchanger. Heat transfer medium inlet 22a and heat transfer mediumoutlet 22 b are disposed in wall 22 to provide for the flow of a heattransfer medium HTM, commonly steam, to and from heat exchanger 30.Housing 20 can be made of various suitable materials compatible withtypical operating conditions of evaporators. In one embodiment, housing20 is comprised of a stainless steel pipe with flanges 23, made of thesame material, threaded or welded thereto.

Turning now to heat exchanger 30 and considering its structure indetail, the heat exchanger comprises a bank of spaced-apart tube plates32 as illustrated in FIGS. 1-3. As seen particularly in FIGS. 2 and 3,the bank of tube plates 32 forms an array of elongated tubes 33including openings 33 a through which liquid L may flow. An upperportion of tubes 33 form the heat exchanger liquid inlet, and a lowerportion forms the heat exchanger product liquid and vapor outlet. Tubeplates 32 are formed into a unitary structure disposed within housing 20and interconnected by plates 38 a, 38 b, and 38 c. Plates 38 a, 38 b,and 38 c each include one or more openings 38 s formed to receive tubeplates 32 and to secure the tube plates in a desired configuration.

Each tube plate 32 is fabricated from a pair of corrugated sheets 34 and35 as illustrated in FIGS. 4 and 5. It is useful to consider in somedetail the morphology of the pair of corrugated sheets 34 and 35 moreparticularly shown in FIG. 4. Each corrugated sheet 34 and 35 is of agenerally undulating, or wavy, structure with a series of alternatingconcave segments 34 a, 35 a and convex segments 34 b, 35 b forming aseries of valleys and ridges. Viewed interiorly of sheets 34 and 35 inFIG. 4, concave segment 34 a forms a valley in sheet 34, and convexsegment 34 b forms an adjacent ridge. In corrugated sheet 35, shownopposite sheet 34 in FIG. 4, concave segment 35 a forms a valley insheet 35 and convex segment 35 b forms an adjacent ridge. Corrugatedsheets 34 and 35 are aligned and brought into contact with each other bymoving, for example, sheet 35 in the direction indicated by the arrowsin FIG. 4 so that opposed valleys formed by concave segments 34 a and 35a form tubes 33 with openings 33 a bounded in part by abutting convexsegments 34 b and 35 b as shown in FIG. 5. It is appreciated that anynumber of tubes 33 of various sizes may comprise a tube plate 32,depending on the size and spacing of the segments 34 a, 35 a, 34 b, and35 b which may be selected for corrugated sheets 34 and 35. Corrugatedsheets 34 and 35 are welded or otherwise sealed and secured together atsides or edges 36 a and 36 b. Plates 38 a, 38 b, and 38 c, discussedbelow, along with the pressure of heat transfer medium HTM passingbetween the tube plates 32 tend to urge the convex segments 34 b, 35 btogether. (See FIG. 6) Corrugated sheets 34 and 35 may be of anymaterial suitable for the environment and operating conditions of theevaporator 10, and in one embodiment comprises stainless steel.

As can be appreciated from an examination of FIGS. 2, 3, and 6, tubeplates 32 are held in a spaced-apart arrangement by plates 38 a, 38 b,and 38 c. The spacing between adjacent tube plates 32 forms passageways36 through which the heat transfer medium HTM flows. Moreover, plates 38a, 38 b, and 38 c with tube plates brace the tube plates 32 so as tomaintain the shape of the tubes when exposed to pressure. Each plate 38a, 38 b, and 38 c, in one embodiment, is formed from generally flatsheet material similar in composition and thickness to that ofcorrugated sheets 34 and 35 of the tube plates 32, although the platesare not limited to this material and thickness. Moreover, additionalplates of similar design may be used, depending on the length of thetube plates 32. Factors considered in selecting the material for plates38 a, 38 b, and 38 c and in determining the need for additional platesmay include the operating pressures and manner of connecting the platesto tube plates 32 and to wall 22 where appropriate. Each plate 38 a, 38b, 38 c includes a series of spaced apart and shaped slots 38 s (seeFIG. 2) wherein each slot is shaped so that it will fit the undulationsof a tube plate 32, allowing space for thermal expansion. In a commonmanufacturing arrangement, these slots 38 s can be made using a CNCmachining process. Likewise, the plates 38 a, 38 b, and 38 c may, in oneembodiment, be welded to the tube plates 32 using CNC welding based onthe same template as that used to machine slots 38 s. In this way,relatively thin material may be used for plates 38 a, 38 b, and 38 c andtube plates 32.

End plates 38 a and 38 c along with housing wall 22 effectively enclosethe interior 25 of the housing where heat exchanger 30 is disposed andthrough which the heat transfer medium HTM flows. End plates 38 a and 38b are secured and sealed to wall 22 of housing 20 by any of a number ofconventional means. It is appreciated that the pressure within interior25 is greater that the pressure within tubes 33 and this difference inpressure tends to urge sheets 34 and 35 of each tube plate 32 together.In one embodiment the intermediate plate 38 b may assume an alternatedesign. In this case the plate is provided with a relatively largecentral opening that receives and holds the entire bank of tube plates32. Here, each tube plate is not completely surrounded with an opening38 s. Rather, plate 38 b tends to engage each tube plate 32 aboutopposite ends 36 a and 36 b. Furthermore, with this alternate design,plate 38 b may be connected to wall 22 of the housing 20.

Focusing now on the vapor collector, indicated generally by the numeral40, as shown in FIGS. 1 and 3, the vapor collector comprises a ductstructure 42 extending at least partially underneath heat exchanger 30.A vapor inlet 42 c is disposed in a lower portion of duct structure 42with at least a portion thereof generally facing downward. Ductstructure 42 forms a vapor outlet 44 which is operably connected to asource of reduced pressure 46 which may comprise a vacuum pump, blower,or other device to provide a reduced pressure to draw vapor V from theevaporator 10. In one embodiment of the present invention, a portion ofthe duct structure 42 may be omitted and a vapor outlet provided in thewall 22 of housing 20. In this case, vapor V emitted by the heatexchanger 30 is drawn from the evaporator 10 via the vapor outlet.

A reservoir 50 is disposed beneath vapor collector 40 to collect productliquid PL. Conventional means are used to remove collected productliquid PL for further processing, end use, or disposal. In oneembodiment, multiple evaporators 10 are operated in a modularapplication, to be described below, and reservoir 50 associated with oneevaporator is fluidly connected to liquid container 21 of anotherevaporator.

An anti-splash device 60 is disposed between vapor collector 40 andreservoir 50. In one embodiment, anti-splash device 60 comprises achevron-type structure including a series of steeply-angled plates 62 asillustrated in FIG. 1. Each angled plate 62 is angled at a relativelysmall angle with respect to the general direction of flow of productliquid PL. The angle and spacing of the angled plates in this embodimentare such that in general there is no vertical line-of-sight from withinreservoir 50 through anti-splash device 60. Other forms of ananti-splash device 60 can be utilized. Principally, the anti-splashdevice 60 functions to permit product liquid PL drops to pass therethrough under the influence of gravity, but interfere with or deflectproduct liquid droplets (backsplash) that splash upwardly from thesurface of the product liquid in reservoir 50 and prevent suchbacksplash droplets from being entrained in the vapor stream beinginduced into the vapor collector 40.

As has been mentioned above, two or more evaporators 10 may be arrangedand interconnected in a modular fashion. Connecting evaporators 10 in amodular fashion provides economies of design and manufacture associatedwith producing overall evaporator designs to meet a wide range of needs.In one embodiment, illustrated schematically in FIG. 7, three evaporatormodules EM_(A), EM_(B), and EM_(C) are connected in an example of amultiple effect arrangement. Module EM_(A), EM_(B), and EM_(C) aresupplied in parallel with heat transfer medium HTM. Liquid L is suppliedto evaporator module EM_(A) which produces vapor V_(A) and productliquid PL_(A). Vapor V_(A) is collected and product liquid PL_(A) flowsthrough an anti-splash device to evaporator module EM_(B). Productliquid PL_(A) is evaporated in evaporator module B producing vapor V_(B)and product liquid PL_(B). Vapor V_(B) is collected from evaporatormodule EM_(B) and product liquid PL_(B) flows through an anti-splashdevice to evaporator module EM_(C) where it is further evaporatedproducing vapor V_(C) and product liquid PL_(C). Vapor V_(C) iscollected from evaporator module EM_(C) and product liquid PL_(C) flowsthrough an anti-splash device into a reservoir and is the final productliquid output of the modular arrangement. Another embodiment of amultiple effect arrangement is shown in FIG. 8 showing an example ofthree evaporator modules connected in a different manner. Heat transfermedium HTM is supplied only to evaporator module EM_(A) while vaporV_(A) is used as the heat transfer medium for evaporator module EM_(B).Similarly, vapor V_(B) is used as the heat transfer medium forevaporator module EM_(C). It is appreciated that in this embodiment aswell, an anti-splash device is employed with each vapor collector toprevent backsplash as product liquid PL flows from one evaporator moduleto another. A further embodiment comprises a single effect modulararrangement. In a single effect arrangement, multiple heat exchangersare stacked such that product liquid and vapor generated by one heatexchanger are supplied together to a next heat exchanger for furtherevaporation prior to vapor separation. FIG. 9 shows an example of thisembodiment in a case of using three heat exchangers in series Liquid Lis supplied to heat exchanger module HE_(A). Heat transfer medium HTMflowing through heat exchanger HE_(A) evaporates a portion of liquid Lproducing a mixed-phase flow of product liquid PL_(A) and vapor V_(A).The mixed-phase flow from heat exchanger HE_(A) is supplied to heatexchanger HE_(B) where PL_(A) is further evaporated and product liquidPL_(B) and vapor V_(B) are produced. The mixed product liquid PL_(B) andvapor V_(B) are supplied to heat exchanger HE_(C) from which productliquid PL_(C) and vapor V_(C) are produced. The final productliquid-vapor stream is supplied to a vapor collector and anti-splashdevice to separate out vapor V_(C) and deposit product liquid PL_(C).

An example of typical modules in terms of the tube plates used isrepresented in Table 1. This example shows seven modules ranging fromModule I consisting of 5 tube plates with two tubes per plate. Module Iis 0.8 ft in diameter (largest cross section) at 1 ft in lengthproviding 5.4 ft² of heat transfer area. The example modules I-VII rangefrom 5.4 to 12,500 ft² of heat transfer area. Module IV, for example, iscomprised of 22 tube plates, each plate having 10 tubes. The overalldiameter, or module diameter, of the bank of tube plates in module IV is3.3 feet, and the module is 2.6 feet long and comprises 340 ft² of heattransfer area.

TABLE 1 Example tube plate bank modules # # Tubes Module Module ModuleTube per diameter length area Module Plates plate ft ft ft² I 5 2 0.81.0 5.4 II 9 3 1.3 1.5 21.5 III 14 5 2.0 2.3 85 IV 22 10 3.3 2.6 340 V32 14 4.6 5.2 1,333 VI 48 21 6.9 9.8 5,570 VII 65 28 9.2 13.1 12,500

As shown in Table 2 below, evaporation of up to 500,000 lbs/hr of waterwith heat flux between 15,000 and 2,250 BTU/hr,sq.ft. can be achievedwith a limited number of modules by stacking up to four modules in asingle effect arrangement. For example, to evaporate of 25,000 lb/hr ofwater requires 2 8,750,000 BTU/hr heat duty. Using a heat flux of 9,000BTU/hr ft², for example, a heat transfer area of 2,972 ft² is required.From Table 1, it is seen that three V modules will provide 1,333 ft²each for a total of 3,999 ft². Thus, three V modules would be selectedas the combination formed from among the seven modules giving thesmallest and therefore least expensive modular assembly providing therequired area

TABLE 2 Modular Selection for ranges of water evaporation rates and heatfluxes Area required, ft² # Modules & Module ID for Given Flux H₂0 HeatEvaporation, Duty, Flux, BTU/hr ft² 1000 lb/hr  1000 BTU/hr 15,00012,000 9,000 7,500 6,000 5,000 4,500 3,750 3,000 2,250 1 535 36 45 59 7189 107 119 143 178 238 2 × II 2 × II 3 × II 4 × II 2 × III 2 × III 2 ×III 2 × III 3 × III 3 × III 1 1,070 71 89 119 143 178 214 238 285 357476 4 × II 2 × III 2 × III 2 × III 3 × III 3 × III 3 × III 4 × III 1 ×IV 2 × IV 3 2,675 178 223 297 357 446 535 594 713 892 1189 3 × III 3 ×III 4 × III 2 × IV 2 × IV 2 × IV 2 × IV 3 × IV 3 × IV 4 × IV 5 5,350 357446 594 713 892 1070 1189 1427 1783 2378 2 × IV 2 × IV 2 × IV 3 × IV 3 ×IV 4 × IV 4 × IV 2 × V 2 × V 2 × V 10 10,700 713 892 1189 1427 1783 21402378 2853 3567 4756 3 × IV 3 × IV 4 × IV 2 × V 2 × V 2 × V 2 × V 3 × V 3× V 4 × V 25 26,750 1783 2229 2972 3567 4458 5350 5944 7133 8917 11889 2× V 2 × V 3 × V 3 × V 4 × V 4 × V 1 × VI 2 × VI 2 × VI 2 × VI 50 53,5003567 4458 5944 7133 8917 10700 11889 14267 17833 23778 3 × V 3 × V 2 ×VI 2 × VI 2 × VI 2 × VI 3 × VI 3 × VI 4 × VI 2 × VII 100 107,000 71338917 11889 14267 17833 21400 23778 28533 35667 47556 2 × VI 2 × VI 3 ×VI 3 × VI 4 × VI 4 × VI 4 × VI 3 × VII 3 × VII 4 × VII 250 267,500 1783322292 29722 35667 44583 2 × VII 2 × VII 3 × VII 3 × VII 4 × VII 500535,000 35667 44583 3 × VII 4 × VII

Considering now the general operation of evaporator 10 and referring tothe figures, especially FIG. 1, a liquid L to be evaporated is suppliedto liquid container 21. Liquid L is caused to flow into openings 33 a oftubes 33 by gravity or other means to assure adequate film developmenton the interior surfaces of tubes 33. Heat transfer medium HTM issupplied to inlet 22 a and flows more or less continuously within andthrough interior 25 of housing 20, within the heat exchanger, and outoutlet 22 b. As heat transfer medium HTM flows within heat exchanger 30,the medium flows through passageways 36 (FIG. 6) between tube plates 32heating liquid L and producing vapor V and product liquid PL. Vapor V isdrawn downward by the action of reduced pressure source 46 such thatproduct liquid PL and vapor V together flow downward, out of heatexchanger 30 and towards vapor collector 40. In one embodiment, productliquid PL and vapor V flow around and downwardly past an upper portion42 a of vapor collector 40. Vapor V is drawn upwardly into vapor inlet42 c by the reduced pressure developed by reduced pressure source 46while product liquid PL continues to fall towards reservoir 50. Vapor Vis thus collected. In another embodiment, the portion of duct structure42 of vapor collector extending across housing 20 is omitted. In thisembodiment, vapor V is drawn laterally through a vapor outlet formed inthe housing 20 under the influence of reduced pressure source 46.Product liquid PL flows through anti-splash device 60 and into reservoir50. Droplets of backsplash may be caused by drops of product liquid PLimpacting the surface of the product liquid PL in the reservoir 50.Because the reduced pressure source 46 creates a relatively low pressurein the vapor collector 40, droplets of backsplash tend to becomeentrained in the vapor being induced into the vapor collector. However,the presence of anti-splash device 60 tends to deflect the backsplashdroplets and cause them to fall back and settle into reservoir 50. Morespecifically, drops of product liquid PL falling from heat exchanger 30pass through the openings between plates 62, while droplets ofbacksplash contain insufficient mechanical energy to pass upwardlythrough anti-splash device 60 and are diverted by plates 62 and causedto settle back into reservoir 50.

The present invention may, of course, be carried out in other specificways than those herein set forth without departing from the scope andthe essential characteristics of the invention. The present embodimentsare therefore to be construed in all aspects as illustrative and notrestrictive and all changes coming within the meaning and equivalencyrange of the appended claims are intended to be embraced therein.

1. An evaporator for evaporating a liquid, comprising: a. a housing; b.a heat exchanger for transferring heat from a heat transfer medium tothe liquid and producing a vapor and a product liquid; c. a vaporcollector disposed substantially within the housing and including avapor inlet having a downward-facing portion; and d. wherein the vaporproduced by the heat exchanger flows downwardly past an upper portion ofthe vapor collector and upwardly into the vapor inlet.
 2. The evaporatorof claim 1 wherein the heat exchanger includes a liquid inlet, an outletfor product liquid and vapor, and a bank of tube plates with each tubeplate including a pair of corrugated sheets secured together whereineach corrugated sheet includes a series of alternating concave andconvex segments with adjacent segments being generally mirror images ofeach other, and wherein the corrugated sheets comprising each tube plateare disposed such that each concave segment of one sheet faces a concavesegment of the other sheet, and wherein each convex segment of one sheetcontacts or lies closely adjacent a convex segment of the other sheetand wherein the tube plates are spaced apart and spacing the tube platesincludes bracing the tube plates with two or more plates with each platehaving openings shaped to generally conform to the tube plates andthereby adapted to retain the shape of each tube plate when exposed topressure.
 3. The evaporator of claim 1 comprising a reservoir disposedbelow the vapor collector to receive the product liquid, and ananti-splash device disposed between the vapor collector and thereservoir for preventing backsplash of product liquid from a surface ofthe product liquid in the reservoir into the vapor collector.
 4. Theevaporator of claim 3 wherein the heat exchanger includes a liquidinlet, an outlet for product liquid and vapor, and a bank of tube plateswith each tube plate including a pair of corrugated sheets securedtogether wherein each corrugated sheet includes a series of alternatingconcave and convex segments with adjacent segments being generallymirror images of each other, and wherein the corrugated sheetscomprising each tube plate are disposed such that each concave segmentof one sheet faces a concave segment of the other sheet, and whereineach convex segment of one sheet contacts or lies closely adjacent aconvex segment of the other sheet
 5. The evaporator of claim 1 whereinthe heat exchanger comprises a plurality of tube plates with each tubeplate being adapted to receive the liquid; and, wherein the tube platesare spaced apart to form a series of passageways for permitting the heattransfer medium to flow there between.
 6. The evaporator of claim 5wherein each tube plate includes a pair of corrugated sheets securedtogether so as to form a series of elongated tubes oriented verticallytherein.
 7. The evaporator of claim 1 wherein the vapor collectorincludes a duct that extends transversely below the heat exchanger. 8.The evaporator of claim 1 wherein a source of reduced pressure isoperatively connected to the vapor collector for maintaining a fluidpressure within the vapor collector less than a fluid pressure withinthe heat exchanger.
 9. The evaporator of claim 1 wherein the evaporatorincludes a series of modules with each module including at least a heatexchanger.
 10. The evaporator of claim 9 wherein the modules are stackedone above another in a generally vertical arrangement.
 11. An evaporatorfor evaporating a liquid, comprising: a. a housing; b. a heat exchangerfor evaporating a portion of the liquid and generating a product liquidand a vapor; c. a vapor outlet disposed below at least a portion of theheat exchanger for permitting vapor to exit the housing; d. a reservoirdisposed below the vapor outlet to receive the product liquid; and, e.an anti-splash device disposed between the vapor outlet and thereservoir for preventing backsplash of product liquid from a surface ofthe product liquid in the reservoir into the vapor outlet.
 12. Theevaporator of claim 11 wherein the heat exchanger includes a liquidinlet, an outlet for the product liquid and vapor, and a bank of tubeplates with each tube plate including a pair of corrugated sheetssecured together wherein each corrugated sheet includes a series ofalternating concave and convex segments with adjacent segments beinggenerally mirror images of each other, and wherein the corrugated sheetscomprising each tube plate are disposed such that each concave segmentof one sheet faces a concave segment of the other sheet, and whereineach convex segment of one sheet contacts or lies closely adjacent aconvex segment of the other sheet.
 13. The evaporator of claim 11including a vapor collector disposed generally between the heatexchanger and the reservoir and including a vapor inlet having adownward-facing portion.
 14. The evaporator of claim 11 including avapor collector extending transversely within the housing and betweenthe heat exchanger and the reservoir and wherein the vapor collectorincludes a vapor inlet including a downward facing portion.
 15. Theevaporator of claim 11 wherein the anti-splash device comprises a seriesof spaced-apart plates.
 16. The evaporator of claim 15 wherein theplates are disposed in a parallel relationship and slightly angled withrespect to the general direction of product liquid flow.
 17. Theevaporator of claim 11 wherein the anti-splash device comprises a meshstructure.
 18. The evaporator of claim 11 wherein the vapor outlet formsa part of a vapor collector disposed substantially within the housingand above the anti-splash device.
 19. The evaporator of claim 18 whereinthe vapor collector includes a vapor inlet having a downward-facingportion and communicating fluidly with the vapor outlet.
 20. Anevaporator for evaporating a liquid, comprising: a. a housing; b. a heatexchanger to evaporate a portion of a liquid to produce a product liquidand a vapor; c. a vapor outlet disposed below a substantial portion ofthe heat exchanger; d. wherein the heat exchanger includes: i) a liquidinlet; ii) an outlet for product liquid and vapor; iii) a bank ofspaced-apart tube plates with each tube plate including a pair ofcorrugated sheets secured together; iv) each corrugated sheet includinga series of alternating concave and convex segments with adjacentsegments being generally mirror images of each other; v) wherein thecorrugated sheets are disposed such that each concave segment of onesheet faces a concave segment of the other sheet, wherein each convexsegment of one sheet contacts or lies closely adjacent a convex segmentof the other sheet; and vi) wherein the heat exchanger includes one ormore vertically spaced-apart horizontal plates, each plate having one ormore openings for receiving the tube plates.
 21. The evaporator of claim20 including a vapor collector disposed substantially within the housingand including a vapor inlet having a downward-facing portion.
 22. Theevaporator of claim 20 comprising a reservoir disposed below the vaporoutlet to receive the product liquid and an anti-splash device disposedbetween the vapor outlet and the reservoir for preventing backsplash ofproduct liquid from a surface of the product liquid in the reservoirinto the vapor outlet.
 23. The evaporator of claim 20 including a vaporcollector including a vapor inlet having a downward-facing portion andthe vapor collector disposed substantially within the housing, areservoir disposed below the vapor collector to receive the productliquid, and an anti-splash device disposed between the vapor collectorand the reservoir for preventing backsplash of product liquid from asurface of the product liquid in the reservoir into the vapor collector.24. The evaporator of claim 20 wherein the inlet is disposed at a topportion of the heat exchanger and the outlet is disposed at a bottomportion of the heat exchanger; and, wherein the elongated tubes extendbetween the top and bottom portions.
 25. The evaporator of claim 20including at least a pair of spaced apart plates with each plate havinga series of openings therein for receiving the tube plates, and whereinthe openings within the plates maintain the tube plates in spaced apartrelationship so as to define passageways between the tube plates forpermitting the heat transfer medium to flow.
 26. The evaporator claim 20wherein one or more plates interconnect the tube plates and form aunitary structure.
 27. The evaporator of claim 20 including a pair ofvertically spaced-apart horizontal plates with each plate including oneor more openings shaped to generally conform to the tube plates andthereby adapted to retain the shape of the tube plates when exposed topressure.
 28. The evaporator of claim 20 wherein a first plate isdisposed at a top portion of the heat exchanger and is secured to thetube plates and to a wall of the housing; and, wherein a second plate isdisposed at a bottom portion of the heat exchanger and is secured to thetube plates and to the wall of the housing, thereby forming a closedspace between the first and second plates and within the housing. 29.The evaporator of claim 20 wherein the housing includes a heat transfermedium inlet and a heat transfer medium outlet for accommodating theflow of the heat transfer medium within the heat exchanger.
 30. Theevaporator of claim 20 wherein the vapor outlet forms a part of a vaporcollector disposed substantially within the housing.
 31. The evaporatorof claim 30 wherein the vapor collector is communicatively connected tothe vapor outlet and includes a vapor inlet having a downward-facingportion.
 32. The evaporator of claim 30 including a reservoir disposedbelow the vapor collector for receiving the product liquid.
 33. Theevaporator of claim 32 including an anti-splash device disposed betweenthe vapor collector and the reservoir for preventing product liquid fromsplashing from the reservoir into the vapor outlet.
 34. A method ofevaporating a liquid comprising: a. flowing the liquid through anevaporator comprising a housing, a heat exchanger, and a vaporcollector; b. heating the liquid by flowing a heat transfer mediumthrough the heat exchanger and producing a product liquid and a vapor;and c. directing the product liquid and vapor downwardly past an upperportion of the vapor collector and inducing the vapor upwardly into thevapor collector.
 35. The method of claim 34 wherein inducing the vaporupwardly into the vapor collector includes providing a reduced pressuresource to reduce the pressure in the vapor collector and draw the vaporthrough a downward-facing vapor inlet disposed in the vapor collector.36. A method of evaporating a liquid comprising: a. flowing the liquidinto a heat exchanger; b. heating the fluid by flowing a heat transfermedium through the heat exchanger and producing a product liquid and avapor with the product liquid falling into an underlying reservoir; c.inducing the vapor through a vapor outlet associated with theevaporator; and d. preventing product liquid backsplash droplets frombeing entrained with the vapor and entering the vapor outlet.
 37. Themethod of claim 36 wherein preventing backsplash droplets from enteringthe vapor outlet includes deflecting the droplets by an anti-splashdevice and causing the droplets to settle back into reservoir.
 38. Amethod of fabricating an evaporator comprising: a. constructing a heatexchanger having a bank of spaced-apart tube plates with each tube plateincluding two corrugated sheets with each sheet having alternatingconcave and convex segments, b. securing the two corrugated sheets ofeach tube plate together by aligning the concave and convex segments andaffixing and sealing opposite edges of the two corrugated sheetstogether such that the convex segments abut or lie in close proximity toeach other and the concave segments form tubes for generally containinga product liquid and a vapor; c. spacing adjacent formed tube plates soas to define passageways there between for permitting a heat transfermedium to move between the tube plates; and, d. wherein spacing adjacentformed tube plates includes bracing the tube plates with two or moreplates with each plate having openings shaped to generally conform tothe tube plates and thereby retain the shape of each tube plate whenexposed to pressure
 39. The method of claim 38 including disposing avapor collector, in the form of a duct transversely below the heatexchanger wherein the duct includes a closed end, open end, and adownward-facing vapor inlet.
 40. The method of claim 38 includingpositioning an anti-splashback device below a vapor collector forpreventing backsplash droplets of the liquid product from entering thevapor collector which is disposed between the heat exchanger and areservoir.